does anyone know what the stock spring rates for a 99 (or corisponding body style) are.

im going to order a set of coil overs front and rear with costume rates but need to know the stock ones so i know where to start.

was thinking 400 front and 300 rear since these cars weigh over 3,000 pounds i dont think it would be to stiff.

 

You are way off. Not stiff enough in the front (well maybe depends on what you are trying to do and what shocks) and WAY too stiff in the rear. And based on your statement I have to wonder what shocks, because if they are drag shocks, you can forget them working decently for handling, let alone with that kind of spring rate.

Stock 292/115 or so. Strano Performance Lowering springs are well proven and well balanced are 550/150.

 

well i was thinking koni yellows for shocks.

im going to lower it like 2in. i picked those spring rates because most of the ppl i know and cars iv driven (given they where imports) usually stop at around 350 or 450 front and rear and there pretty stiff but there like 1/4 of an inch from hitting there tires on 25-2800 lb cars.

so what where you thinking more like 500 front 250 rear? or still go stiffer ?

 

The spring rates used for one car are for that particular car...it is tied directly to that car's suspension geometry, not yours. For example, I just put new springs and shocks on my Viper, and they use 8" 500lb/in springs up front and 8" 800 lb/in springs out back. If you tried those rates in an f-body, you'd be close for the fronts, but you wouldn't be able to stand the rears. It would handle and ride like **** too...lots of oversteer.

He gave you rates to shoot for (550 lb/in fronts, 150 lb/in rears), but keep in mind that lowering an f-body 2 inches will put you very close to your bump stops, and is far from optimal for handling. If you don't care about handling, disregard what I just said.

 

i wont be tracking the car or racing but i do drive rough/aggressive weather it be a strait line around corners or changing lanes in heavy traffic.

if stock rear is 115ish going to 150 dosnt seam like a big difference im assuming these cars dont squat or roll much in the back then?? or do they have a major over steer problem around corners???(only had mine 2 weeks and shocks are blown and bouncy and the springs are sagging so im not sure how they handle when in good condition)

i want a realy firm borderline to stiff ride but i dont want that ride that makes ppls fillings fall out of there teeth. but i defenaly dont want to bottom out with the 2in or more of drop.

 

If you don't want to bottom out with a 2" drop, especially in the back, you will have to go with a much higher spring rate. How much higher? Not sure, but drop it that much and take a gander at the bump stops and how close they are to the axle tubes...if they aren't touching already, they are likely close.

The springs generally recommended for decent handling lower the car about 1.25" front and rear, and use the rates spec'd above. You can lower it more, but you'll be doing it for the looks, not performance. Sam's suggestions were what I used on my '02 Camaro, and it was a nice, firm ride, but wasn't harsh at all. Handled really well too.

Leave the slammed look to the imports...if they claim that their cars handle better because of it, they likely have no clue what they are talking about. Lowering an f-body is a compromise between looks and performance...you can't necessarily have both, but a 1.25" drop is way better than the stock 4x4 look.

 

You need to seriously search.
You also need to understand (like both of these guys are saying) not all cars have the same suspension geometry. The cars you are used to probably have struts in the front, and IRS in the rear. We have short/long A-arm suspension (coilover) in the front, and solid axle in the rear. Our suspension will move/articulate differently, and the spring rates will reflect that. Spring rates that work well for this application will likely not work well with others.
I can let Sam explain more about his own experience but I know from reading his posts he tried A LOT of different rates and setups to get to what he preferred (and won multiple national champions with).
Before you go off assuming "550lbs/in front, wow thats really stiff right?" No, not at all for our cars, these are great for the street as well as racing. Some road race guys are running closer to 700-1000lbs/in front...
And "150lbs/in rear, thats too soft right"? Wrong again. These are solid axle cars, going overly stiff will be like driving on ice, especially with big power. There is not a lot of weight back there (45% roughly give or take), a and ton of effortless torque, you need grip, so softer rates work. Some road race guys will be running 200-300lbs/in in the rear, but those are the guys that are also running 700-1000lbs/in front, and usually capped on power (under 300RWHP) so they want that extra rate to help rotate the car.
I have his setup (koni SAs, Strano springs, strano swaybars, fays2 watts link) and all I can say is wow, totally different car. Ridiculousness balanced, easy to drive hard at the limit and just tons of grip and feedback. Very good on the street as well, front certainly isn't overly stiff.

Here you can see Sam driving his said Camaro, good enough to pass a 911 GT3... Remember this isn't a caged, gutted race car either.
And auto-xing the same car: